1. Field of the Invention
The present invention relates to the inhibition of the use of a mobile radio communication device when it is lost or stolen and to the smooth recovery of the mobile radio communication device.
2. Related Arts
Recently, many demands are being placed on mobile radio communication devices, which serve as "whenever, wherever and with whomever" communication means, and in consonance with technical developments, there has been a rapid increase in the degree of freedom of use afforded by their portability and in the number of them that are in use. An example arrangement of such a mobile radio communication device is described in Japanese Unexamined Patent Publication No. Hei 8-140142, and an explanation will be given for a PHS (Personal Handy Phone System) portable mobile station while referring to a block diagram in FIG. 1. In FIG. 1, reference numeral 41 denotes a power source controller; 42, a voice processor; 43, a TDMA controller; 44, a radio controller; 45, a radio unit; 46, a battery; 47, a main controller; 48, a memory; 49, a display; 50, a key operation unit; 51, a transmitter/receiver, which uses a loudspeaker and a microphone; 52, an antenna; 53, a transmission controller; and 54, a timer.
The main controller 47 is connected to the individual sections 41 to 46, sections 48 to 51, and sections 53 and 54, excepting only section 52, the antenna, and controls the entire mobile station in consonance with a control program stored in the memory 48. In consonance with the operational state of the mobile station, the power source controller 41 precisely turns on and off the power supplied to the battery 46 or to the individual sections. For example, since no sound is required while dialing using the key operation unit 50, the supply of power to the power source system, such as the voice processor 42, is halted.
The voice processor 42 processes voice signals received at the antenna 52 and outputs speech through the loudspeaker of the transmitter/receiver 51. In addition, the voice processor 42 processes voice input through the microphone of the transmitter/receiver 51 and outputs it from the antenna 52, and generates an audible alarm via the transmitter/receiver 51.
The TDMA controller 43 performs a time-sharing process for a TDMA system using a signal that is received from the voice processor 42 or the radio controller 44. The radio controller 44 controls radio functions, and the radio unit 45 converts transmission signals into radio frequencies, and also converts reception signals into intermediate frequencies.
The display 49 employs a liquid crystal display process to display telephone numbers, transmitted by the key operation unit 50, and guidance that is consonant with key operation commands and alarms. The transmission regulator 53 controls transmissions in consonance with the setup of a secret ID number using the key operation unit 50, or controls transmissions in consonance with a transmission control start time and a transmission control end time that are input using the key operation unit 50. The timer 54 transmits the transmission control start time and end time to the transmission controller 53.
When the thus arranged mobile station is powered on, the mobile station measures the strength of the electric field of signals that are transmitted by surrounding base stations, and then acquires control channel data from the nearest base station and enters the standby state in consonance with the control channel data that is acquired. When a transmission request, such as the input of a telephone number, is issued by the key operation unit 50, the mobile station performs predetermined procedures for transmission to the base station. When transmissions by a mobile station that has been lost or stolen are to be controlled to prevent its unauthorized use, a method exists for controlling transmissions using a secret ID number, or for controlling transmissions within an arbitrary time period. According to this method, a secret ID number is input using the key operation unit 50, with transmission being inhibited as long as the secret ID number is not input or when the transmission regulator 53 does not recognize a secret ID number that is input; or the control start time and end time are input by using the key operation unit 50, and in consonance with the input, the transmission controller 53 inhibits transmissions within a time period indicated by the timer 54. When the condition for inhibiting automatic transmissions is time period control, it is difficult for multiple home users to set time periods for the inhibition of transmissions by a mobile station. In addition, when a transmission must be made while transmission inhibition is in effect, another operation is required to permit transmissions and communication activities and to reset the transmission control time. As a result, such an operation is complicated and resetting of a transmission control time period may be forgotten.
To eliminate this shortcoming, a transmission controller is provided for a mobile station. When a user inputs a specific code to place a mobile station in a transmission control mode, code recognition means identifies the specific code that is input as code that is used to establish a transmission control mode and the controller places the mobile station in a transmission control mode that corresponds to the specific code. When a user inputs a telephone number that is not to be targeted by transmission control, the telephone number that is input is recorded by telephone number setting means. Then, when the user inputs a period of time during which transmission control is to be effective for transmissions to telephone numbers other than the one mentioned above, the input time is set by time setting means. Following this, if a third party initiates a transmission to a telephone number other than the one set by the telephone number setting means, the transmitted telephone number comparison means detects this and determines that the telephone number entered for the transmission differs from that set by the telephone number setting means. As a result, the timer means begins to measure the elapsed communication time. When the elapsed time exceeds the time that is set by the time setting means, the transmission controller imposes transmission control and places the mobile station in the off-hook state.
An explanation will now be given for a means employed to search for a mobile station that has been lost. First, an audible alarm of the lost mobile station can be generated by calling the mobile telephone using a mobile telephone communication mode. A specific mobile station ID (inherent number) wait setting unit and a transmission control release failure recognition unit are provided for the transmission control. In the condition where the ID is set at the mobile station and transmission is restricted, the specific mobile station ID wait setting unit identifies a failure in the release of transmission control when an inadequate operation for the release of the inhibition of transmission is performed at predetermined times. When a failure is identified, the main controller 47 places the mobile station in a mobile station intercommunication wait state and reduces reception sensitivity to a predetermined level. Further, the main controller 47 generates an audible alarm emitted at maximum amplification by the loudspeaker. As part of the mobile station search performed by the thus arranged mobile station, an ID input by the key operation unit 50 is set; whether or not transmission is inhibited is determined; the input code recognition means determines whether code input by the key operation unit 50 is valid; the inhibition of transmissions is released when the code input is a secret ID number for the release of such transmissions; the main controller identifies the unauthorized use and places the mobile station in the mobile station inter-communication wait state when the count of invalid codes input reaches five or more; a variable ATT or AGC in the radio unit 5 is controlled to reduce reception sensitivity to a predetermined level; an audible alarm, a buzzing sound, generated at the loudspeaker is adjusted to the maximum amplification; and the searching mobile station approaches a mobile station to be searched for and reduces reception sensitivity to a range wherein an audible alarm, a buzzing sound, can be received, to enable the easy detection of the mobile station that is searched for. It should be noted in this explanation that the mobile station has a function for switching from a normal system for communication with a base station to an abnormal system for communication with a mobile station.
Not only such a search for a mobile radio communication device, but also dialing limit means that functions when a radio device is lost or stolen, and a display control method for giving a warning message are proposed in Japanese Unexamined Patent Publication No. Hei 4-272995.
However, according to the prior art, when a mobile radio communication device is misplaced, lost or stolen, its unauthorized use by a third party can not be prevented. Even when a mobile radio communication device is in the hands of a third party who is acting in good faith and a dialing limit has been set, there is no way by which the third party can identify the owner, and accordingly, it takes time for the device to be returned to the owner.